TITLE: GCN CIRCULAR
NUMBER: 24161
SUBJECT: GRB 190422A: Fermi GBM detection
DATE: 19/04/23 22:20:03 GMT
FROM: Rachel Hamburg at UAH
R. Hamburg (UAH), C. Fletcher (USRA), and C. Meegan (UAH)
report on behalf of the Fermi GBM Team:
"At 22:58:24.00 UT on 22 April 2019, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 190422A (trigger 577666709 / 190422957)
which was also detected by the Swift/BAT (Moss et al. 2019, GCN 24147).
The GBM on-ground location is consistent with the Swift position.
The angle from the Fermi LAT boresight at the GBM trigger time is 71
degrees.
The GBM light curve shows a complex lightcurve with one main peak
preceded and followed by weaker bursts of emission.
A duration (T90) is calculated to be about 212 s (50-300 keV).
The time-averaged spectrum from T0-21.5 s to T0+42.0 s is
best fit by a power law function with an exponential
high-energy cutoff. The power law index is -1.67 +/- 0.09 and
the cutoff energy, parameterized as Epeak, is 58 +/- 7 keV.
A Band function fits the spectrum equally well with
Epeak = 50 +/- 9 keV, alpha = -1.57 +/- 0.14 and
beta = -2.42 +/- 0.27.
The event fluence (10-1000 keV) in this time interval is
(4.8 +/- 0.3)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+1.54 s in the 10-1000 keV band
is 4.84 +/- 0.17 ph/s/cm^2."
The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog:
https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html
For Fermi GBM data and info, please visit the official Fermi GBM Support
Page:
https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/